Manufacturing method for film-covered electrical device

ABSTRACT

In a vacuum container ( 2 ), a bag-shaped laminate film ( 12 ) containing a battery element ( 11 ) and having an opening ( 12   a ) is pinched at positions corresponding to two principal surfaces ( 11   a ) of the battery element ( 11 ), the battery element ( 11 ) having a positive layer and a negative layer stacked via a separator. Pressure in the vacuum container ( 2 ) is reduced. An electrolytic solution ( 20 ) is poured from an electrolytic-solution supply line ( 4 ) into the bag-shaped laminate film ( 12 ) through the opening ( 12   a ) with pressure in the vacuum container ( 2 ) kept reduced until the entire battery element ( 11 ) is immersed in the electrolytic solution ( 20 ). The reduced pressure in the vacuum container ( 2 ) is increased to make the battery element ( 11 ) absorb the electrolytic solution ( 20 ) by means of the difference in pressure.

TECHNICAL FIELD

The present invention relates to a manufacturing method andmanufacturing apparatus for a film-covered electrical device, which isan electrical device element contained in laminate film, typified by abattery or capacitor.

BACKGROUND ART

Electrical devices typified by batteries and electrolytic capacitors aremanufactured by filling a case which is made of metal or the like andwhich contains an electrode group with an electrolytic solution and thensealing the case, where the electrode group is an electrical deviceelement.

Conventionally, a case placed upright is filled with a predeterminedamount of electrolytic solution and left at rest for an extended periodof time to allow the electrolytic solution to gradually permeate spacesin the electrode group. However, since an electrode group is generallymade of electrode plates stacked densely, it takes time to allow theelectrolytic solution to permeate the spaces in the electrode group. Thecase needs to be left at rest, for example, for a whole day and night inorder for the electrolytic solution to permeate the spaces among theelectrodes on its own. This means very inefficient production.

Also, since the electrolytic solution is absorbed very slowly, if therequired amount of electrolytic solution is supplied at once into thecase, the electrolytic solution will overflow the case. Methods adoptedto deal with this situation include a method in which a watertight coveris placed on an opening of the case and filled with a predeterminedamount of electrolytic solution. However, the method involves placingthe covers one by one on the cases, making it difficult to increasemanufacturing efficiency.

Japanese Patent No. 3467135 discloses an electrolytic-solution fillingmethod intended to solve this problem. The method depressurizes anopening of a case, fills the opening with the electrolytic solution totemporarily form a pool, fills the depressurized case with theelectrolytic solution, allows the electrolytic solution to permeatespaces in an electrode group, and then increases pressure in the case tomake the electrolytic solution in the pool permeate the spaces in theelectrode group.

By depressurizing the case once, the method expels air from the spacesin the electrode group so that the air will not obstruct permeation ofthe electrolytic solution. After creating a condition in which theelectrode can permeate the spaces easily, the method fills the case withthe electrolytic solution. Then, the method further pressurizes the caseto cause the electrolytic solution in the pool to permeate. Thecombination of depressurization and pressurization not only reduces thetime required for the electrolytic solution to be absorbed, but alsoprevents the electrolytic solution from spattering upon pressurerelease.

DISCLOSURE OF THE INVENTION

In addition to electrical devices which use a metal case, film-coveredelectrical devices which use a laminate material for outer covering havebeen developed, where the laminate material is a thin film created bylaminating a metal layer of aluminum or the like and heat-fusible resinlayers via adhesive layers. Generally, laminate materials have astructure in which a thin metal layer of aluminum or the like has bothsides coated with a thin resin layer. The laminate materials areresistant to acid and alkali, and are lightweight and flexible.

However, the laminate film for film-covered electrical devices hasflexibility, unlike metal cases. That is, the laminate film, whichdeforms easily, has a problem not encountered by metal cases whichhardly deforms when filled with an electrolytic solution.

The electrolytic solution that is poured into an opening of the laminatefilm flows into between principal surfaces of the electrical deviceelement and the laminate film without forming a pool at the opening.This is because the laminate film is flexible. Thus, the methoddisclosed in Japanese Patent No. 3467135 cannot be adopted as it is,where the method seals the electrical device element temporarily fromthe outside by means of the pool and impregnates the electrolyticsolution forming the pool into the electrical device element by means ofthe pressure difference between the electrical device element and theoutside.

Also, the electrolytic solution is not impregnated into the electrodegroup at uniform speed, but is impregnated irregularly depending on thearea to be impregnated. The irregular impregnation with the electrolyticsolution appears as creases in the surfaces of the laminate film due tothe flexibility of the laminate film.

Also, the irregular impregnation with the electrolytic solutionpartially produces, on the surfaces, areas with low ionic conductivitybetween positive and negative layers, resulting in reduced electricalperformance characteristics of the battery. Besides, since the laminatefilm deforms easily, binding forces between electrode layers are weak,and consequently the irregular impregnation can cause separators to becreased.

In view of the above circumstances, an object of the present inventionis to provide a manufacturing method and manufacturing apparatus for afilm-covered electrical device, where the manufacturing method andapparatus are capable of filling the film-covered electrical device withan electrolytic solution in a short time without causing irregularimpregnation when impregnating the electrolytic solution or producingcreases in separators.

To achieve the above object, the present invention provides amanufacturing method for a film-covered electrical device, comprising:holding, in a vacuum container, a bag-shaped laminate film that containsa power generating element and that has an opening, by pinching thebag-shaped laminate film at positions corresponding to two principalsurfaces of the power generating element, the power generating elementhaving a positive layer and a negative layer stacked via a separator;reducing pressure in the vacuum container; pouring an electrolyticsolution into the bag-shaped laminate film through the opening with thepressure in the vacuum container kept reduced until the entire powergenerating element is immersed in the electrolytic solution; andincreasing the reduced pressure in the vacuum container.

The present invention makes it possible to fill the laminate film withthe electrolytic solution in a short time without producing creases inthe separator.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing a configuration of a fillingapparatus used to fill a film-covered battery according to the presentinvention with an electrolytic solution;

FIG. 2 is a sectional view showing an example of a holding fixtureaccording to the present invention;

FIG. 3 is a perspective view showing another example of a holdingfixture according to the present invention;

FIG. 4 is a schematic perspective view of battery elements illustratinga principal surface and edge surfaces of the battery elements;

FIG. 5 is a graph showing a relationship between the time required forfilling and amount of the electrolytic solution absorbed into element,where a pushing force on the principal surface is used as a parameter;

FIG. 6A is a perspective view of a film-covered electrical device whichis an application example of the present invention;

FIG. 6B is a front view of a film-covered electrical device which isanother application example of the present invention;

FIG. 6C is a schematic diagram of a battery element accommodated in alaminate film as viewed in the direction of a principal surface toillustrate pooling conditions of the electrolytic solution;

FIG. 7 is a schematic diagram of a battery element divided into fourareas into which the electrolytic solution permeates through respectivefour edge surfaces;

FIG. 8A is a schematic diagram illustrating how the electrolyticsolution is absorbed through the edge surfaces in a final stage offilling;

FIG. 8B is a schematic diagram showing how the electrolytic solutionpooled at top and on both sides has been absorbed before theelectrolytic solution pooled in the bottom is absorbed;

FIG. 8C is a schematic diagram showing how the electrolytic solutionpooled at top and on both sides is being absorbed after the electrolyticsolution pooled in the bottom has been absorbed;

FIG. 9 is a schematic diagram showing an example of a system forsupplying an electrolytic solution to bag-shaped laminate filmcontaining a plurality of battery elements;

FIG. 10 is a schematic diagram showing another example of a system forsupplying an electrolytic solution to bag-shaped laminate filmcontaining a plurality of battery elements;

FIG. 11 is a schematic diagram showing another example of a system forsupplying an electrolytic solution to bag-shaped laminate filmcontaining a plurality of battery elements;

FIG. 12 is a schematic diagram showing another example of a system forsupplying an electrolytic solution to bag-shaped laminate filmcontaining a plurality of battery elements;

FIG. 13 is a schematic diagram showing an example of a mechanism formaintaining the laminate film in an open state;

FIG. 14A is a schematic diagram showing another example of a mechanismfor maintaining the laminate film in an open state;

FIG. 14B is a schematic diagram illustrating a configuration and traveldirections of claws in the mechanism shown in 14A;

FIG. 15A is a schematic diagram showing another example of a mechanismfor maintaining the laminate film in an open state;

FIG. 15B is a schematic diagram illustrating a configuration and traveldirections of claws in the mechanism shown in 15A;

FIG. 16 is a schematic diagram showing an example of a mechanism forcleaning that part of laminate film which is to be heat-fused;

FIG. 17 is a schematic diagram showing another example of a mechanismfor cleaning that part of laminate film which is to be heat-fused; and

FIG. 18 is a flowchart illustrating a manufacturing method for afilm-covered electrical device according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, an embodiment of the present invention will be described withreference to the drawings.

FIG. 1 is a schematic diagram showing a configuration of a fillingapparatus used to fill a film-covered battery according to the presentinvention with an electrolytic solution.

(Film-Covered Battery)

First, a configuration of film-covered battery 10 according to thepresent embodiment will be outlined.

Film-covered battery 10 includes battery element 11, a positivecollector and negative collector installed on battery element 11, anouter cover made of one sheet of laminate film 12 and containing batteryelement 11 together with electrolytic solution 20, a positive tabconnected to the positive collector, and a negative tab connected to thenegative collector.

Battery element 11 includes a plurality of positive plates and negativeplates stacked alternately via separators.

Herein, regarding battery element 11, surfaces perpendicular to astacking direction will be referred to as principal surfaces 11 a andsurfaces parallel to the stacking direction will be referred to as edgesurfaces 11 b, as shown in FIG. 4.

Each positive plate is made of aluminum foil coated with a positiveelectrode while each negative plate is made of copper foil coated with anegative electrode. Extension strips, which extend from a stack area,are not coated with electrode material. The extension strips from thepositive plates are joined together by ultrasonic welding, and so arethe extension strips from the negative plates, to form, respectively,the positive collector and negative collector which are relays. At thesame time, the positive tab is connected to the positive collector andthe negative tab is connected to the negative collector also byultrasonic welding.

One sheet of laminate film 12 is folded into two to surround batteryelement 11 by sandwiching battery element 11 from both sides in thethickness direction of battery element 11. Laminate film 12 is alaminate of heat-fusible resin layer, a metal layer, and a protectivelayer. With the heat-fusible resin layers of PP (polypropylene) placedfacing the battery, laminate film 12 seals battery element 11 as theheat-fusible resin layers are fused together by heat.

Electrolytic solution 20 is prepared using 1 mol/liter of LiPF₆ as asupporting electrolyte and a mixture of propylene carbonate and ethylenecarbonate (ratio by mass is 50:50) as a solvent.

(Filling Apparatus)

Next, a configuration of filling apparatus 1 according to the presentembodiment will be described.

Filling apparatus 1 includes vacuum container 2, holding fixture 3,electrolytic-solution supply line 4, evacuation line 5, gas inlet line6, and controller 7.

Controller 7 controls the operation of holding fixture 3, a vacuum pump(not shown) connected to evacuation line 5, and liquid delivery system41 connected to electrolytic-solution supply line 4. Operation of thecomponents controlled by controller 7 will be described in detail below.

Vacuum container 2 houses holding fixture 3. Wall surfaces of vacuumcontainer 2 are connected with electrolytic-solution supply line 4,evacuation line 5, and gas inlet line 6.

Holding fixture 3 holds bag-shaped laminate film 12 by pinching laminatefilm 12 from both sides (both principal surfaces 11 a) in the thicknessdirection of battery element 11 when electrolytic solution 20 is filledinto bag-shaped laminate film 12 containing battery element 11.

Preferably a space (V_(L) in FIG. 6C) is provided below battery element11 to pool electrolytic solution 20 as described later, and thus it ispreferable to place battery element 11 above bottom surface 12 b oflaminate film 12, with a space provided therebetween. As shown in FIG.6B, positive tab 104 a and negative tab 104 b connected to batteryelement 11 face away from each other. Furthermore, positive tab 104 aand negative tab 104 b are fixed in place beforehand, being sealed inlaminate film 12. Consequently, since battery element 11 is supported bypositive tab 104 a and negative tab 104 b, battery element 11 can bepositioned, being separated from bottom surface 12 b of laminate film12.

However, laminate film 12 of film-covered battery 10 is flexible.Consequently, if electrolytic solution 20 is poured without laminatefilm 12 being supported in some way or other, electrolytic solution 20will flow around to principal surfaces 11 a of battery element 11without pooling on the sides of edge surfaces 11 b of battery element11. Also, this may cause the separators to be creased if the batteryelement is impregnated irregularly with electrolytic solution 20.

Thus, holding fixture 3 pinches laminate film 12 at positionscorresponding to principal surfaces 11 a of battery element 11. Thisprevents poured electrolytic solution 20 from flowing around toprincipal surfaces 11 a of battery element 11 and allows electrolyticsolution 20 to be pooled once, surrounding edge surfaces 11 b of batteryelement 11. Besides, even if the battery element is impregnatedirregularly with electrolytic solution 20, holding fixture 3 holds downbattery element 11 via laminate film 12 at positions corresponding toprincipal surfaces 11 a of battery element 11, thereby preventing theseparators from being creased.

Now, a configuration example of holding fixture 3 and a method forholding laminate film 12 and battery element 11 will be described moreconcretely.

FIG. 2 shows an example of holding fixture 3. Holding fixture 3A shownin FIG. 2 includes a plurality of plate members 3 a fixedly placed atpredetermined intervals. The intervals between plate members 3 a formsockets 3 b which receive bag-shaped laminate film 12 containing batteryelement 11.

FIG. 3 shows another example of holding fixture 3. Holding fixture 3Bshown in FIG. 3 has a structure in which fixed end plate 3 d and aplurality of movable plates 3 e placed at predetermined intervals aremounted on a base 3 f. Fixed end plate 3 d is mounted at an end of base3 f. A plurality of movable plates 3 e are arranged parallel to fixedend plate 3 d. Fixed end plate 3 d is fixed to base 3 f. On the otherhand, movable plates 3 e are installed in such a way as to be movable onbase 3 f. Piston 3 c is installed on the side opposite to fixed endplate 3 d. Piston 3 c pushes movable plate 3 e mounted at the endopposite to fixed end plate 3 d.

As shown in FIG. 3, pieces of bag-shaped laminate film 12 containingbattery element 11 are inserted one each between fixed end plate 3 d andmovable plate 3 e or between each pair of adjacent movable plates 3 e.When piston 3 c pushes movable plates 3 e, pushing force is applied tobag-shaped laminate film 12 containing battery element 11. That is,holding fixture 3B can adjust pushing force on film-covered battery 10during filling with the electrolytic solution.

Incidentally, in FIG. 1, bag-shaped laminate film 12 containing batteryelement 11 is pinched by holding fixture 3 in such a way that positivetab 104 a and negative tab 104 b described later will face in adirection perpendicular to the plane of the paper.

Laminate film 12 containing battery element 11 and being pinched byholding fixture 3 has been shaped like a bag. That is, laminate film 12is heat-fused on three sides other than the side along which laminatefilm 12 is folded. Specifically, laminate film 12 has been heat-fused onthe two sides from which positive tab 104 a and negative tab 104 bextend, but the side opposite the folded side has not yet beenheat-fused. Laminate film 12 is bag-shaped to allow electrolyticsolution 20 to be poured through the side has not yet been heat-fusedwith the side serving as opening 12 a. That is, in FIG. 1, holdingfixture 3 pinches bag-shaped laminate film 12 from both sides in thethickness direction of battery element 11 with the unfused side up insuch a way that positive tab 104 a and negative tab 104 b will face inthe direction perpendicular to the plane of the paper. Incidentally,although one sheet of laminate film 12 folded into two is taken as anexample according to the present embodiment, the present invention isnot limited to this and two sheets of laminate film may be usedalternatively. In that case, the laminate film is shaped like a bag inadvance by heat-fusing three sides.

One end of electrolytic-solution supply line 4 is connected to a tank(not shown) which stores the electrolytic solution. The other end isinstalled on an upper wall of vacuum container 2, being positioned suchthat electrolytic solution 20 supplied through electrolytic-solutionsupply line 4 can be poured through opening 12 a of laminate film 12which opens upward.

Evacuation line 5, which is used to evacuate vacuum container 2, hasvalve 5 a and vacuum pump 5 b.

Gas inlet line 6 is used to introduce dry air or inert gas into vacuumcontainer 2 evacuated by evacuation line 5 and thereby break the vacuumin vacuum container 2. Gas inlet line 6 includes valve 6 a and a gasstorage tank (not shown).

(Pressure Range of Pushing Force)

Next, description will be given of a pressure range of the pushing forceexerted by holding fixture 3 on film-covered battery 10 which is beingfilled with the electrolytic solution.

If excessive pressure is applied by holding fixture 3 to principalsurfaces 11 a of battery element 11, battery element 11 will be squeezedexcessively, preventing electrolytic solution 20 from infiltrating thebattery element. Consequently, pores in the separators and electrodescannot be impregnated with electrolytic solution 20. This is becauseelectrolytic solution 20 enters the battery element mainly by seepinginto contact surfaces of the separators and electrodes by capillaryaction, and the application of too much pressure makes it difficult forthe solution to infiltrate the contact surfaces. On the other hand, ifthe applied pressure is too low, spaces may be formed among positiveplates, separators, and negative plates, electrolytic solution 20 mayinfiltrate into the spaces, causing the separators to lose firmness orbecome creased, and the creases may remain after the battery iscompleted.

A relationship between the time required for filling and amount of theelectrolytic solution absorbed into element is shown in FIG. 5, where apushing force on the principal surface is used as a parameter.

FIG. 5 shows measurement results obtained by a filling method which usesthe pressure difference and measurement results obtained by a fillingmethod which does not use a pressure difference. The filling methodwhich uses a pressure difference is a method in which electrolyticsolution 20 pooled at locations facing edge surfaces 11 b is sucked bythe negative pressure of battery element 11 kept under vacuum. Thismethod is a feature of the present invention and will be described indetail later. On the other hand, the method which does not use apressure difference is a method which causes battery element 11 to beimpregnated with electrolytic solution 20 by gravity, by the capillaryaction of the contact surfaces between the electrodes and separators,and by the capillary action of the pores in the separators withoutcreating any pressure difference between the inside and outside ofbattery element 11.

Regarding the filling method which uses a pressure difference, anexperiment was conducted under two conditions: the pushing force ofholding fixture 3 was set to 0.25 kPa and 0.5 kPa. Regarding the fillingmethod which does not use a pressure difference, the experiment wasconducted only under one condition: the pushing force of holding fixture3 was set to 0.5 kPa.

It can be seen from FIG. 5, that the time required for filling with aprescribed amount of electrolytic solution is shorter when the pressureof 0.25 kPa is applied than when the pressure of 0.5 kPa is applied. Atfirst, battery element 11 is impregnated with the electrolytic solutionat approximately the same rate under 0.25 kPa and 0.5 kPa, but towardthe end of filling, i.e., when the prescribed amount of electrolyticsolution has been almost filled, the impregnation rate slows down andthus a longer time is required for filling when the higher pressure of0.5 kPa is used. In short, if the pushing force exerted by holdingfixture 3 is too high, a longer time will be required for filling.

However, even if the same pressure of 0.5 kPa is used, the fillingmethod which uses a pressure difference can finish filling in a farshorter time than the filling method which does not use a pressuredifference.

In the above experiment, to prevent the impregnation rate from slowingdown toward the end of filling, the pushing force of the holding fixturemay be reduced gradually as the filling proceeds from the initial stageto the end of impregnation. Also, the pushing force of the holdingfixture may be reduced to almost zero near the end of impregnation.

(Electrolytic-Solution Filling Method)

Next, a method of filling with electrolytic solution 20 using fillingapparatus 1 according to the present embodiment will be described withreference to a flowchart of FIG. 18.

The method of filling with electrolytic solution 20 according to thepresent embodiment fills battery element 11 with electrolytic solution20 using a pressure difference. The following procedures are used forfilling with electrolytic solution 20.

First, in vacuum container 2, filling apparatus 1 pinches laminate film12 containing battery element 11 using holding fixture 3 and therebyholds the entire principal surfaces of battery element 11 (Step S1).When laminate film 12 is held by holding fixture 3, the top side oflaminate film 12 containing battery element 11 forms opening 12 a whichremains to be heat-fused.

Next, with valve 5 a open, filling apparatus 1 operates vacuum pump 5 bof evacuation line 5 to depressurize vacuum container 2 (Step S2). Whena predetermined degree of vacuum is reached, filling apparatus 1 closesvalve 5 a. In this state, the pressures in vacuum container 2 and inbattery element 11 contained therein have equally been reduced to apredetermined level.

Next, using a mechanism for maintaining an open state (described later),filling apparatus 1 maintains opening 12 a of laminate film 12 in anopen state (Step S3).

Next, filling apparatus 1 supplies electrolytic solution 20 throughelectrolytic-solution supply line 4 (Step S4) and pours suppliedelectrolytic solution 20 through opening 12 a at the top of laminatefilm 12 (Step S5). Incidentally, the supplying of electrolytic solution20 through electrolytic-solution supply line 4 will be described indetail later. Since battery element 11 has its entire principal surfacesheld in the thickness direction by holding fixture 3, there is no spacefor electrolytic solution 20 to flow in on the sides of principalsurfaces 11 a. Also, since battery element 11 is held by holding fixture3, there is little space among the positive plates, separators, andnegative plates for electrolytic solution 20 to flow in. Furthermore,the pressures in vacuum container 2 and in battery element 11 containedtherein have equally been reduced to a predetermined level.Consequently, electrolytic solution 20 is not sucked into batteryelement 11 by negative pressure in battery element 11. Electrolyticsolution 20 is poured until entire battery element 11 is immersed inelectrolytic solution 20. Consequently, electrolytic solution 20 ispooled on the sides of edge surfaces 11 b of battery element 11. Thatis, of the six surfaces of battery element 11, four surfaces—top,bottom, and two lateral edge surfaces—excluding principal surfaces 11 aare surrounded by electrolytic solution 20.

Next, filling apparatus 1 opens valve 6 a of gas inlet line 6 tointroduce gas into vacuum container 2, and thereby increases thepressure in vacuum container 2 (Step S6). Although the introduction ofgas raises the pressure in vacuum container 2, the inside of batteryelement 11 surrounded by electrolytic solution 20 remains depressurizedas a result of evacuation. Consequently, there is a pressure differencebetween the inside of battery element 11 surrounded by electrolyticsolution 20 and the inside of vacuum container 2. That is, since thereis a vacuum in battery element 11, electrolytic solution 20 is suckedinto battery element 11 by the negative pressure, thereby fillingbattery element 11 with electrolytic solution 20 rapidly.

Moreover, although electrolytic solution 20 enters through four edgesurfaces 11 b, since the entire principal surfaces of battery element 11are held by holding fixture 3, electrolytic solution 20 does not enterthrough the principal surfaces. This prevents the separators from beingcreased. In the above example, holding fixture 3 holds the entire areasof principal surfaces 11 a of battery element 11, and this is mostdesirable. However, the operation and effect of the present inventioncan be achieved even if there are areas which are not held by holdingfixture 3 in part of principal surfaces 11 a. For example, most parts ofprincipal surfaces 11 a including the centers may be held, leavingperipheral parts.

Incidentally, if the amount of electrolytic solution 20 which can bepooled around edge surfaces 11 b is less than the amount required forfilm-covered battery 10, the above processes may be repeated beginningwith the process of pouring electrolytic solution 20 until the requiredamount is reached. Also, the process of pouring the electrolyticsolution and the process of raising the pressure in vacuum container 2may be performed simultaneously. One of the processes may be performedcontinuously while the other process is performed intermittently.

As described above, although flexible laminate film is used as coveringmaterial for the battery, the method of filling with electrolyticsolution 20 according to the present invention can keep laminatedsurfaces taut and flat, prevent the separators from being creased duringfilling with electrolytic solution 20, and carry out filling rapidly.

(Pooling Conditions of Electrolytic Solution)

Next, pooling conditions of electrolytic solution 20 according to thepresent embodiment will be described with reference to FIGS. 6A to 6C.

Battery element 11 is impregnated with electrolytic solution 20 throughedge surfaces 11 b of battery element 11. Battery element 11, which isrectangular in shape, has four edge surfaces 11 b. To reduce the fillingtime and prevent creasing of laminate film 12, it is important to fillbattery element 11 with electrolytic solution 20 using all four edgesurfaces 11 b effectively.

FIG. 6A is a perspective view of a film-covered electrical device whichis an application example of the present invention. Extension strip 43made of metal foil and used to draw electric current extends from theelectrode in each layer of battery element 11. Extension strips 43 ofthe positive layers are connected to positive tab 104 a in positivecollector 103 a. Similarly, extension strips 43 of the negative layersare connected to negative tab 104 b in negative collector 103 b. Thefilm-covered electrical device shown in FIG. 6A has recess 12 e formedin laminate film 12 to house battery element 11. The film-coveredelectrical device shown in FIG. 6A is a type in which two sheets oflaminate film are stacked face to face and the four sides are sealed.

However, the film-covered electrical device according to the presentinvention may use flat laminate film without a recess. Alternatively,the present invention may be applied to a film-covered electrical deviceof a type in which three sides are sealed by folding a single sheet oflaminate film. A front view of such an example is shown in FIG. 6B. InFIG. 6B, bottom surface 12 b is folded to form a side.

FIG. 6C, which is a schematic diagram of a battery element accommodatedin a laminate film as viewed in the direction of a principal surface,illustrates pooling conditions of the electrolytic solution. FIG. 6Cshows a part surrounded by sides 12 a, 12 b, 12 c, and 12 d (sides 12 cand 12 d correspond to inner borders of sealing) in FIG. 6B.Incidentally, positive tab 104 a, negative tab 104 b, extension strips43, positive collector 103 a, and negative collector 103 b are omittedin FIG. 6C.

Regarding the size of battery element 11, the length is denoted by L andthe width is denoted by W. Inner space of laminate film 12 is larger insize than battery element 11. Electrolytic solution 20 is pooledtemporarily in spaces produced by the size difference. Each space isformed by one of edge surfaces 11 b of battery element 11 and sealed end12 f closest to edge surface 11 b or the bend of the laminate film.Hereinafter, the volumes of the spaces will be referred to as poolingvolumes.

In FIG. 6C, the pooling volumes on both sides of film-covered battery 10placed in a vertical position are denoted by V_(W) and the poolingvolume at the bottom is denoted by V_(L).

Pooling volumes V_(W) of two spaces are shown in FIG. 6C: the spaceformed by left edge surface 11 b and left sealed end 12 f, and the spaceformed by right edge surface 11 b and right sealed end 12 f. That is,pooling volumes V_(W) are volumes of the spaces formed between the edgesof laminate film 12 and two edge surfaces 11 b which join the other twoedge surfaces 11 b of battery element 11—edge surface 11 b located atopening 12 a and edge surface 11 b located at the bottom (opposite toedge surface 11 b located at opening 12 a).

On the other hand, pooling volume V_(L) is the volume of space formed byedge surface 11 b at the bottom and the bend of laminate film 12 (thebase of laminate film 12). That is, pooling volume V_(L) is the volumeof space formed between an edge of laminate film 12 and one of edgesurfaces 11 b of battery element 11, i.e., bottom edge surface 11 bopposite to edge surface 11 b located at opening 12 a.

The upper border of V_(W) is flush with the upper end of battery element11. Also, pooling volumes V_(W) and pooling volume V_(L) are bounded bylines each of which joins a corner of battery element 11 and a corner oflaminate film 12. If there are some other objects in the spaces, thevolumes occupied by the objects are deducted. Examples of the otherobjects as mentioned here include extension strips 43, positivecollector 103 a, and negative collector 103 b in FIG. 6B as well asinsulating coating members covering the collectors.

A necessary condition for pooling electrolytic solution 20 on a side ofedge surface 11 b located at opening 12 a, i.e., in the upper part, isgiven by:0<2V _(W) +V _(L) <V _(TOTAL)  (1)where V_(TOTAL) is the total volume of electrolytic solution 20 pouredinto laminate film 12 during filling.

On the other hand, a condition for filling electrolytic solution 20 intothe separators not only through edge surface 11 b at opening 12 a, butalso through edge surfaces 11 b on both sides and at the bottom is givenby:0<V _(W′)0<V _(L)  (2)To pour electrolytic solution 20 through all four edge surfaces 11 b, itis necessary to satisfy condition equations (1) and (2).

Next, the amounts of electrolytic solution 20 absorbed through four edgesurfaces 11 b—edge surface 11 b at opening 12 a, edge surfaces 11 b onboth sides, and edge surface 11 b at the bottom—will be estimated. FIG.7 shows a schematic diagram of battery element 11 divided into fourareas into which electrolytic solution 20 permeates through respectivefour edge surfaces 11 b.

Area S_(W) is a surface area of the area into which electrolyticsolution 20 infiltrates through each of edge surfaces 11 b on bothsides. Area S_(L) is a surface area of the area into which electrolyticsolution 20 infiltrates through edge surface 11 b at opening 12 a oredge surface 11 b at the bottom. Area S_(W) and area S_(L) are given asfollows using length L and width W:S _(W)=½×W/2×W=W ²/4  (3)S _(L) =WL/2−W ²/4  (4)

The ratio between the amounts of electrolytic solution 20 absorbedthrough two groups of edge surfaces 11 b per unit time is given by:S _(W) :S _(L) =W ²/4:(W/2)·(L−W/2)=W/2:L−W/  (5)

When electrolytic solution 20 is absorbed through all four edge surfaces11 b, ideally absorption through all four edge surfaces 11 b will befinished simultaneously.

It is not desirable that absorption of electrolytic solution 20 throughedge surfaces 11 b on both sides be finished earlier than absorptionthrough edge surface 11 b at the bottom. Reasons for this will bedescribed with reference to FIGS. 8A and 8B.

At a stage shown in FIG. 8A, filling with electrolytic solution 20 iscarried out through all four edge surfaces 11 b. Then, it is assumedthat the filling proceeds to its final stage shown in FIG. 8B. In FIG.8B, electrolytic solution 20 pooled above edge surface 11 b at opening12 a and in the spaces of pooling volume V_(W) on both sides has beenabsorbed. On the other hand, electrolytic solution 20 pooled in thespace of pooling volume V_(L) on a side of edge surface 11 b at thebottom has not yet been absorbed. Electrolytic solution 20 remaining atthis time has to be absorbed only through edge surface 11 b at thebottom, thus extending the time until the completion of filling.

Even if absorption does not finish all at once, if absorption throughedge surface 11 b at the bottom finishes earlier than absorption throughedge surfaces 11 b on both sides, there is no problem. Reasons for thiswill be described with reference to FIG. 8C.

It is assumed that the filling proceeds to its final stage shown in FIG.8C. In FIG. 8C, electrolytic solution 20 pooled above edge surface 11 bat opening 12 a and electrolytic solution 20 pooled in the space ofpooling volume V_(L) on the side of edge surface 11 b at the bottom havebeen absorbed. On the other hand, electrolytic solution 20 pooled in thespaces of pooling volume V_(W) on both sides has not yet been absorbed.In this case, electrolytic solution 20 remaining in the spaces ofpooling volume V_(W) on both sides flows to edge surface 11 b at thebottom by gravity. Thus, even after all electrolytic solution 20 in thespace of pooling volume V_(L) has been absorbed through edge surface 11b at the bottom, edge surface 11 b at the bottom can absorb electrolyticsolution 20 which flows in without being absorbed through edge surfaces11 b on both sides. This makes it possible to reduce the time requiredfor filling the battery with electrolytic solution 20.

Conditions for at least absorption through edge surface 11 b at thebottom to finish earlier than absorption through edge surfaces 11 b onboth sides are given by:V _(L) /S _(L) ≦V _(W) /S _(W)V _(L)≦(S _(L) /S _(W))·V _(W)V _(L)≦(2/W)·(L−W/2)·V _(W)  (6)

Thus, filling conditions which need to be satisfied in order to fillelectrolytic solution 20 into battery element 11 in a short time aregiven by above condition equations (1), (2), and (6).

(System for Supplying Electrolytic Solution)

Next, a system for supplying an electrolytic solution with the fillingapparatus according to the present embodiment will be described.

In FIG. 1 intended to illustrate a basic configuration of the presentinvention, a single film-covered battery 10 is housed in vacuumcontainer 2 and a single electrolytic-solution supply line 4 isprovided.

FIG. 9 shows an example of a system for supplying an electrolyticsolution to a plurality of film-covered batteries.

A filling apparatus shown in FIG. 9 includes a plurality of holdingfixtures 3, relay containers 30 installed for respective holdingfixtures 3, and needle 4 a connected to electrolytic-solution supplyline 4, all of which are housed in vacuum container 2.

Needle 4 a is installed in such a way as to be able to move aboveholding fixtures 3.

Each relay container 30 has opening 30 a, main body 30 b, and supplyport 30 c. Opening 30 a receives electrolytic solution 20 supplied fromneedle 4 a. Main body 30 b temporarily pools electrolytic solution 20.Supply port 30 c supplies electrolytic solution 20 temporarily pooled inmain body 30 b into bag-shaped laminate film 12 containing batteryelement 11. Relay containers 30 are installed above openings 12 a ofrespective pieces of laminate film 12 and below needle 4 a.

With the present configuration, electrolytic solution 20 is not supplieddirectly into bag-shaped laminate film 12 containing battery element 11.That is, with the present configuration, electrolytic solution 20 issupplied into bag-shaped laminate film 12 via relay containers 30 whichtemporarily pool electrolytic solution 20 supplied from needle 4 a.

According to the present embodiment, electrolytic solution 20 issupplied as follows.

First, needle 4 a supplies electrolytic solution 20 into one relaycontainer 30. Electrolytic solution 20 is pooled in relay container 30and then supplied into bag-shaped laminate film 12. In the meantime,needle 4 a supplies electrolytic solution 20 into adjacent another relaycontainer 30. Electrolytic solution 20 is pooled in given relaycontainer 30 and then supplied into bag-shaped laminate film 12. In thisway, according to the present embodiment, electrolytic solution 20 ispooled in relay containers 30 once before being supplied into bag-shapedlaminate film 12.

As described above, according to the present embodiment, electrolyticsolution 20 is supplied into different pieces of bag-shaped laminatefilm 12 by moving needle 4 a. However, the amount of electrolyticsolution 20 absorbed by battery element 11 can exceed the amount ofelectrolytic solution 20 supplied from traveling needle 4 a. To dealwith this, in supplying electrolytic solution 20 to multiple pieces ofbag-shaped laminate film 12 by moving single needle 4 a, the systempools electrolytic solution 20 temporarily in relay containers 30 whilesupplying electrolytic solution 20 in the meantime to different piecesof bag-shaped laminate film 12 one after another by moving needle 4 a.

FIG. 10 shows another example of a system for supplying an electrolyticsolution to bag-shaped laminate film 12 containing a plurality ofbattery elements 11.

Configuration shown in FIG. 10 is the same as the configuration in FIG.9 except that valve 30 d is installed at supply port 30 c of each relaycontainer 30. According to the present configuration, electrolyticsolution 20 is temporarily pooled in relay containers 30 with valves 30d closed and when electrolytic solution 20 is pooled in all relaycontainers 30, electrolytic solution 20 can be supplied into differentpieces of bag-shaped laminate film 12 all together by opening all valves30 d at once. This makes it possible to supply electrolytic solution 20into different pieces of bag-shaped laminate film 12 uniformly withoutbeing affected by the traveling speed of needle 4 a, the supply rate ofelectrolytic solution 20 that is supplied by needle 4 a, the supply rateof electrolytic solution 20 from relay containers 30, or the like.

FIG. 11 shows another example of a system for supplying an electrolyticsolution to bag-shaped laminate film containing a plurality of batteryelements.

Configuration shown in FIG. 11 is the same as the configuration in FIG.10 except that relay containers 30 are installed externally to vacuumcontainer 2. More specifically, opening 30 a, main body 30 b, and valve30 d of each relay container 30 are installed outside the vacuumcontainer 2 while the tip of supply port 30 c is installed in vacuumcontainer 2.

According to the configurations in FIGS. 9 and 10, since relaycontainers 30 are installed in vacuum container 2, electrolytic solution20 is discharged from relay container 30 by gravity. On the other hand,the present configuration, which can use a pressure difference inaddition to the force of gravity to supply an electrolytic solution, cansupply electrolytic solution 20 into bag-shaped laminate film 12rapidly. That is, with the configuration in FIG. 11, since relaycontainers 30 are exposed to atmospheric pressure while the tip ofsupply ports 30 c are exposed to vacuum, electrolytic solution 20 can besucked into vacuum container 2 under negative pressure.

FIG. 12 shows another example of a system for supplying an electrolyticsolution to a plurality of bag-shaped laminate film containing batteryelements.

In the filling apparatus shown in FIG. 12, electrolytic-solution supplyline 4 includes electrolytic solution tank 42, liquid delivery system41, a plurality of supply pipes 4 b, and changeover valve 40.Electrolytic solution tank 42 pools electrolytic solution 20. Liquiddelivery system 41 delivers electrolytic solution 20 from electrolyticsolution tank 42 to vacuum container 2. Changeover valve 40 is installedbetween liquid delivery system 41 and the plurality of supply pipes 4 b.

In the filling apparatus shown in FIG. 1 and FIGS. 9 to 11,electrolytic-solution supply line 4 has a single supply pipe and asingle needle connected to the supply pipe. According to theconfigurations shown in FIGS. 9 to 11, electrolytic solution 20 issupplied into multiple pieces of bag-shaped laminate film accommodatinga battery element as the single needle is moved. On the other hand,according to the configuration shown in FIG. 12, supply pipes 4 b andneedles 4 a are stationary, and changeover valve 40 is used to switchamong supply pipes 4 b and thus among needles 4 a, and thereby supplyelectrolytic solution 20 in turns. In this way, eliminating the need fora mechanism to move supply pipes 4 b and needles 4 a simplifiesequipment configuration as shown in FIG. 12.

(Mechanism for Maintaining Laminate Film in an Open State)

FIG. 13 shows an example of a mechanism for maintaining laminate film 12in an open state, according to the present embodiment.

A pair of suction apparatuses 50 can maintain laminate film 12 in anopen state by pulling opening 12 a of laminate film 12 from outsideusing vacuum suction.

Next, a method for maintaining an open state on a filling apparatusequipped with suction apparatus 50 will be described.

First, laminate film 12 is sucked while under vacuum in the atmosphere.Next, when laminate film 12 is opened, the needle ofelectrolytic-solution supply line 4 is inserted in opening 12 a.Alternatively, a frame member may be inserted in opening 12 a. After theneedle or frame member is inserted, the suction operation of suctionapparatus 50 may be stopped. Subsequently, electrolytic solution 20 ispoured in an evacuated environment.

FIGS. 14A and 14B show another example of the mechanism for maintaininglaminate film 12 in an open state, according to the present embodiment.

As shown in FIG. 14A, the mechanism for maintaining an open state has aplurality of claws 60 each equipped with hook-shaped tip 61. As shown inFIGS. 14A and 14B, claws 60 include two types arranged alternately:claws movable in the direction of arrow a and claws movable in thedirection of arrow b opposite the direction of arrow a.

Next, a method for maintaining an open state on a filling apparatusequipped with claws 60 will be described.

First, tips 61 of claws 60 are inserted in opening 12 a of laminate film12. Next, claws 60 are moved in direction a and direction b, therebymaintaining laminate film 12 in an open state.

FIGS. 15A and 15B show another example of the mechanism for maintaininglaminate film 12 in an open state, according to the present embodiment.A configuration shown in FIG. 15A maintains an open state using claws 70equipped with tips 71. However, unlike claws 60 in FIGS. 14A and 14B,claws movable in the direction of arrow a and claws movable in thedirection of arrow b are not arranged alternately. That is, as shown inFIG. 15B, claws 70 are placed one each on left and right sides: claw 70movable in the direction of arrow a and claw 70 movable in the directionof arrow b. Tips 71 are shaped such as to entirely cover that part oflaminate film 12 which is to be heat-fused. Thus, even if electrolyticsolution 20 discharged from needle 4 a spatters, the presentconfiguration can prevent spatters 20 a from attaching to that part oflaminate film 12 which is to be heat-fused. In this way, claws 70configured as shown in FIGS. 15A and 15B not only maintains laminatefilm 12 in an open state, but also prevents spatters 20 a ofelectrolytic solution 20 from attaching to laminate film 12, enablingreliable heat fusion.

(Mechanism for Cleaning the Part of Laminate Film that is to be HeatFused)

The present invention includes the process of temporarily poolingelectrolytic solution 20 discharged from needle 4 a on the sides of edgesurfaces 11 b of laminate film 12. Discharged electrolytic solution 20may spatter and attach to that part of laminate film 12 which is to beheat-fused. Attached electrolytic solution 20 may obstruct reliable heatfusion. Thus, it is preferable to wipe off any electrolytic solution 20that is attached to the area to be heat-fused.

FIG. 16 shows an example of a mechanism for cleaning that part oflaminate film which is to be heat-fused.

Cleaning mechanism 85 shown in FIG. 16 has wiper 81 at the tip of shaft80. Preferably, wiper 81 is made of material such as nonwoven fabric orsponge which can be impregnated with electrolytic solution 20. Afterelectrolytic solution 20 is poured, but before heat fusion, cleaningmechanism 85 is inserted in opening 12 a of laminate film 12 and movedin the direction perpendicular to the plane of the paper in FIG. 16 withwiper 81 placed in contact with the area to be heat-fused in laminatefilm 12. This allows wiper 81 to wipe any electrolytic solution 20 offthat area of laminate film 12 which is to be heat-fused.

FIG. 17 shows another example of a mechanism for cleaning that part oflaminate film which is to be heat-fused.

Cleaning mechanism 95 shown in FIG. 17 includes two pulleys 90 andwiping belt 91 installed over pulleys 90. Pulleys 90 can be rotated by adriver (not shown), driving, in turn, wiping belt 91.

A cleaning method using cleaning mechanism 95 will be outlined below.

After electrolytic solution 20 is poured, but before heat fusion, one ofpulleys 90 of cleaning mechanism 95 is inserted in opening 12 a oflaminate film 12.

With wiping belt 91 placed in contact with that area of laminate film 12which is to be heat-fused, cleaning mechanism 95 is moved in thedirection perpendicular to the plane of the paper in FIG. 17.Consequently, wiping belt 91 wipes any electrolytic solution 20 off thatarea of laminate film 12 which is to be heat-fused. Subsequently, beforecleaning any other piece of laminate film 12, pulleys 90 are rotated bya predetermined amount. That is, pulleys 90 are rotated so as to retractthat part of wiping belt 91 which has been contaminated as a result ofcleaning and pulley 90 bring a clean part of wiping belt 91 into contactwith that area of laminate film 12 which is to be heat-fused.

In this way, cleaning mechanism 95 can clean that area of laminate film12 which is to be heat-fused always using an uncontaminated cleaningsurface of wiping belt 91. This ensures more reliable cleaning andthereby enables more reliable heat fusion.

(Method for Heat-Fusing Laminate Film)

According to the present invention, filling with electrolytic solution20 is done in vacuum container 2. Thus, if laminate film 12 isheat-fused with vacuum container 2 evacuated, an additional process ofevacuation can be omitted.

The present invention has been described with reference to anembodiment, but the present invention is not limited to the embodimentdescribed above. It is to be understood that various changes andmodifications which may occur to those skilled in the art may be made tothe configuration and details of the present invention without departingfrom the scope of the present invention.

This application claims priority from Japanese Patent Application No.2008-20951 filed Jan. 31, 2008, which is incorporated herein byreference in its entirety.

The invention claimed is:
 1. A manufacturing method for a film-coveredelectrical device, comprising: holding with a holding fixture, in avacuum container, a bag-shaped laminate film that contains a powergenerating element and that has an opening, and pressing with theholding fixture the bag-shaped laminate film at positions correspondingto entireties of two principal surfaces of the power generating elementso that the holding fixture presses the bag-shaped laminate film ontothe entireties of the principal surfaces of the power generatingelement, the power generating element having a positive layer and anegative layer stacked via a separator wherein in the holding step, edgesurfaces of the power generating element are left free; reducingpressure in the vacuum container; pouring an electrolytic solution intothe bag-shaped laminate film through the opening with the pressure inthe vacuum container kept reduced until the level of the electrolyticsolution becomes higher than the top end of the power generating elementwhile pressure is applied to the bag-shaped laminate film at thepositions corresponding to the entireties of the two principal surfacesof the power generating element so that the electrolytic solution doesnot flow between the principal surfaces and the laminate film wherein inthe pouring step, the electrolytic solution is poured into thebag-shaped laminate film via a relay container; and increasing thereduced pressure in the vacuum container, wherein in the pouring step,the power generating element is kept in a state in which the bag-shapedlaminate film is pressed and held onto the entireties of the twoprincipal surfaces by the holding fixture.
 2. The manufacturing methodfor a film-covered electrical device according to claim 1, wherein inthe pouring step, the electrolytic solution is poured into a pluralityof pieces of the bag-shaped laminate film in sequence or all at once viathe relay container, with the plurality of pieces of the bag-shapedlaminate film each containing a respective said power generatingelement, wherein the plurality of pieces of the bag-shaped laminate filmare in the vacuum container and are pinched at positions correspondingto the two principal surfaces of the respective power generatingelement.
 3. The manufacturing method for a film-covered electricaldevice according to claim 1, wherein the relay container pours theelectrolytic solution from the relay container into the bag-shapedlaminate film using a pressure difference between pressure of theatmosphere and reduced pressure in the vacuum container.
 4. Themanufacturing method for a film-covered electrical device according toclaim 1, wherein the electrolytic solution is supplied byelectrolytic-solution supplier that is movably installed.
 5. Themanufacturing method for a film-covered electrical device according toclaim 4, wherein the electrolytic-solution supplier: includes a poolwhich pools the electrolytic solution and a plurality of needles whichdischarges the electrolytic solution supplied from the pool; andsupplies the electrolytic solution through one needle selected from theplurality of needles as a destination of the electrolytic solutionsupplied from the pool.
 6. The manufacturing method for a film-coveredelectrical device according to claim 1, wherein the opening ismaintained in an open state from the time before pouring of theelectrolytic solution starts until the time when pouring of theelectrolytic solution is finished.
 7. The manufacturing method for afilm-covered electrical device according to claim 6, wherein the openstate is maintained by suction at the opening.
 8. The manufacturingmethod for a film-covered electrical device according to claim 6,wherein the open state is maintained by moving a pair of claws insertedin the opening, in a direction away from each other.
 9. Themanufacturing method for a film-covered electrical device according toclaim 8, wherein the open state is maintained with part to be heat-fusedat the opening being covered by the pair of claws.
 10. The manufacturingmethod for a film-covered electrical device according to claim 1,further comprising removing any the electrolytic solution attached tothe opening.
 11. The manufacturing method for a film-covered electricaldevice according to claim 2, wherein the electrolytic solution issupplied by electrolytic-solution supplier that is movably installed.12. The manufacturing method for a film-covered electrical deviceaccording to claim 3, wherein the electrolytic solution is supplied byelectrolytic-solution supplier that is movably installed.
 13. Themanufacturing method for a film-covered electrical device according toclaim 1, wherein the opening is maintained in an open state from thetime before pouring of the electrolytic solution starts until the timewhen pouring of the electrolytic solution is finished.
 14. Themanufacturing method for a film-covered electrical device according toclaim 1, wherein the opening is maintained in an open state from thetime before pouring of the electrolytic solution starts until the timewhen pouring of the electrolytic solution is finished.